In 1919, the former State Park and Forest Commission obtained an 860 acre parcel located in the Millington section of Haddam. The principle feature of the park, Chapman Falls drops more than sixty feet over a series of steps in a Scotland Schist stone formation. The falls also once powered 'Beebe's Mills' which were named after the original owner. The mills operated until the mid 1890's.

A search for the origin of the name 'Devil's Hopyard' reveals a wide variety of different stories; none of them are verifiable and all are likely to be more fiction than fact. One of the most popular of these stories is about a man named Dibble, who had a garden for growing hops used in the brewing of beer. It seems that through usage, Dibble's Hopyard became Devil's Hopyard. There are records of several farmers having hopyards in the area, but there is no mention of a landowner named Dibble. However, Dibble might have been a tenant.

Another tale focuses on the potholes near the falls, which are some of the finest examples of pothole stone formations in this section of the country. Perfectly cylindrical, they range from inches to several feet in diameter and depth. These potholes were formed by stones moved downstream by the current and trapped in an eddy where the stone was spun around and around, wearing a depression in the rock. When the rock wore itself down, another would catch in the same hole and enlarge it. We know this now, but to the early settlers the potholes were a great mystery that they tried to explain with references to the supernatural. They thought that the Devil has passed by the falls, accidentally getting his tail wet. This made him so mad he burned holes in the stones with his hooves as he bounded away.

The park today offers some of the finest birding in the state and fishermen find the clear, cool stream water an excellent source of brook trout.